The production of vulcanized rubbers modified with lateral polar groups (e.g. OH groups) is known from DE-OS 2 653 144 and from European Patent Application 464 478, for example. According to the above-mentioned patent publications, vulcanized rubbers modified by means of mercaptans such as 2-mercapto-ethanol and thioglycollic acid have better mechanical properties, particularly when containing hydrated silica as a filler, than unmodified vulcanized rubbers containing hydrated silica as a filler. A disadvantage of the processes known from the above-mentioned publications for the production of modified vulcanized rubbers is that the production of modified rubbers and the vulcanization thereof have to be carried out in two separate process steps, which has a significant adverse effect on the process economics.
In addition, organosilanes with a special structure are known from DE-OS 2 255 577, which serve as additives for rubber compounds containing silicate fillers and which have a favourable effect on the properties of the vulcanized materials, in a surprising and definitive manner. The additives described in DE-OS 2 255 577 exert no accelerating effect whatsoever on the vulcanization process; rather, additional amounts of a vulcanization accelerator are necessary to obtain the kinetics and density of cross-linking which are suitable for practical application.
Finally, the production and kinetic behaviour of asymmetric disulphides in vulcanized rubbers are described in Rubber Chem. Technol. 46 (5), pages 1299-1315. The compounds cited therein, such as cyclohexyl-dithiobenzthiazole, contain a cyclohexyl radical, which is non-polar and which is thus not capable of interacting with fillers. Separate tests have shown that these compounds are intrinsically unsuitable for use in vulcanization, on account of their low reactivity and disagreeable odours.